Certain fluoroolefin compounds are known to possess insecticidal and acaricidal activity (see, e.g., U.S. Pat. No. 5,248,834; GB 2,288,803-A; WO 94/06741; WO 97/16067; and U.S. Pat. No. 5,998,673. However, the fluoroolefin compounds disclosed in those patents and patent applications are outside the scope of the present invention. U.S. Pat. No. 5,248,834 generically discloses certain 1-aryl-1-(3-aryl-1,2-difluoroprop-1-enyl)cyclopropane compounds. However, that patent does not provide a method to prepare those compounds. In fact, U.S. Pat. No. 5,248,834 does not provide a method to prepare any fluoroolefin compounds.
1,4-diaryl-2-fluoro-4-cyano-2-butenes and a method for their preparation are described in U.S. Pat. No. 5,998,673. Said compounds are useful as insecticidal and acaricidal agents and for protecting plants from damage caused by insect and acarid attack and infestation. Although a method for the preparation of said agents is known, alternative more effective methods contribute to the enhanced availability of these useful insecticidal and acaricidal agents.
It is, therefore, an object of the present invention to provide a process for the preparation of 1,4-diaryl-2-fluoro-4-cyano-2-butenes.
It is also an object of the present invention to provide intermediates useful in said process.
These and other objects of the present invention will become more apparent from the detailed description thereof set forth below.
The present invention provides a process for the preparation of insecticidal and acaricidal 1,4-diaryl-2-fluoro-4-cyano-2-butene compounds of structural formula I 
wherein
Ar is phenyl optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
1- or 2-naphthyl optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups, or
a 5- or 6-membered heteroaromatic ring optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups;
R is hydrogen, C1-C4alkyl, C1-C4haloalkyl, C3-C6cycloalkyl or C3-C6halocycloalkyl; and
Ar1 is phenoxyphenyl optionally substituted with any combination of from one to six halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
phenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
biphenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
phenoxypyridyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
benzylpyridyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
benzylphenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
benzoylphenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
1- or 2-naphthyl optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups, or
a 5- or 6-membered heteroaromatic ring optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups; or
the optical isomers thereof; or
the cis and trans isomers thereof
which process comprises the following steps:
(a) reacting an intermediate of formula II 
wherein Ar1 is defined as above and X is a nucleophilic replaceabale leaving group, such as halogen, alkylsulphonyloxy or arylsulphonyloxy, especially chloro, bromo, iodo, tosyloxy, mesyloxy or the like, with a cyanide delivering reagent in a first solvent to afford a cyano intermediate of formula III; 
(b) reacting said cyano intermediate III with an aldehyde of formula IV 
in the presence of a base in a second solvent to yield an anion which is acidified to afford a diene of formula V 
and
(c) reacting said diene V with magnesium in the presence of a third solvent.
This invention also provides intermediate dienes of structural formula V.
Although a method for the preparation of insecticidal and acaricidal 1,4-diaryl-2-fluoro-4-cyano-2-butenes is described in U.S. Pat. No. 5,998,673, alternative more effective methods contribute to the enhanced availability of these useful insecticidal and acaricidal agents.
Advantageously, the present invention provides an effective and practical method for the preparation of 1,4-diaryl-2-fluoro-4-cyano-2-butenes of formula I, 
wherein Ar, Ar1 and R are defined as above.
In accordance with the process of the invention intermediate II is treated with a cyanide delivering reagent in a polar aprotic solvent (first solvent) to afford the cyano intermediate III. Cyano intermediate III is reacted with an aldehyde of formula IV in the presence of a base optionally in the presence of a second solvent to yield an intermediate which is acidified to afford a diene of formula V; and said diene V is reacted with magnesium in the presence of a protic solvent (third solvent) to provide 1,4-diaryl-2-fluoro-4-cyano-2-butene I. The process is depicted in Flow Diagram I. 
Intermediate aldehydes IV may be prepared as described in U.S. Pat. No. 5,998,673.
First solvents suitable for use in the inventive process include polar aprotic solvents such as dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone or the like, preferably dimethylsulfoxide.
Second solvents suitable for use in the inventive process include aprotic solvents such as tetrahydrofuran, diethyl ether and the like, preferably tetrahydrofuran.
Third solvents suitable for use in the inventive process include protic solvents such as alkanols, preferably methanol or ethanol.
Cyanide ion delivering reagents include alkali metal cyanides and quarternary ammonium cyanides, preferably sodium cyanide or potassium cyanide.
Bases suitable for use in the inventive process are alkali metal amides, such as lithium amide, lithium dimethylamide, lithium diisopropylamide, sodium bis(trimethylsilyl)amide, magnesiochlorodiethylamide (Et2NMgCl), or the like, preferably lithium diisopropylamide.
Bases may be present in amounts ranging from catalytic to excess amounts such as 10 mole % to 4.0 molar excess.
Acids suitable for use in the process of the invention include strong mineral acids such as HCl, HBr or H2SO4, preferably HCl or H2SO4.
In actual practice, intermediate II, preferably wherein X is Br, is treated with at least one molar equivalent of a cyanide delivering reagent, preferably sodium cyanide, in a polar aprotic solvent, preferably dimethyl sulfoxide, to yield the cyano intermediate III; said cyano intermediate III is treated with aldehyde IV in the presence of a base, preferable an alkali metal amide, preferably lithium diisopropylamide in an aprotic solvent, preferably tetrahydrofuran, to yield an intermediate which on acidification, preferably with hydrochloric acid, affords diene (V); said diene (V) is reacted with magnesium in the presence of a protic solvent preferably an alkanol, preferably methanol, or ethanol, to provide the desired 1,4-diaryl-2-fluoro-4-cyano-2-butene I.
The process depicted in Flow Diagram I provides 1,4-diaryl-2-fluoro-4-cyano-2-butene I having predominantly the (Z)-configuration. Formula I compounds wherein the double bond is in the (E)xe2x80x94configuration may be prepared by isomerizing 1,4-diaryl-2-fluoro-4-cyano-2-butene I which are predominantly in the (Z)xe2x80x94configuration using conventional procedures such as exposure to light.
In formula I above, 5-and 6-membered heteroaromatic rings include, but are not limited to, pyridyl, pyrazolyl, imidazolyl, triazolyl, isoxazolyl, tetrazolyl, pyrazinyl, pyridazinyl, triazinyl, furanyl, thienyl and thiazolyl rings each optionally substituted as described in formula I above.
Exemplary of halogen hereinabove are fluorine, chlorine, bromine and iodine. The terms xe2x80x9cC1-C4haloalkylxe2x80x9d, xe2x80x9cC3-C6halocycloalkylxe2x80x9d and xe2x80x9cC1-C4haloalkoxyxe2x80x9d are defined as a C1-C4alkyl group, a C3-C6cycloalkyl group and a C1-C4alkoxy group substituted with one or more halogen atoms, respectively.
The present invention also provides compounds of formula V wherein the variables have the meanings as defined in formula I. 
In compounds of formulae I and V respective following meanings for groups R are preferred: R is C1-C4alkyl; or C3-C6cycloalkyl especially isopropyl or cyclopropyl.
Compounds of formulae I and V, resp. are [referred. Wjereom Ar denotes phenyl which is substituted by halogen or C1-C4alkoxy.
Preference also is given to compounds of formulae I and V, resp. wherein Ar1 is 3-phenoxyphenyl unsubstituted or substituted with any combination of from one to six halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy, or C1-C4haloalkoxy, 3-biphenyl unsubstituted or substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy.
Moreover, particular preference is given to compounds wherein Ar1 is 3-phenoxyphenyl unsubstituted or substituted with any combination of from one to six halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy, particularly 3-phenoxy-4-halogen-phenyl, 3-(4xe2x80x2-halogen-phenoxy)-phenyl or 3-(4xe2x80x2-halogen-phenoxy)-4-halogen-phenyl.
Compounds of formulae I and V, resp. are especially preferred
wherein
Ar is phenyl optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups;
R is hydrogen, C1-C4alkyl, C1-C4haloalkyl, C3-C6cycloalkyl or C3-C6halocycloalkyl;
Ar1 is 3-phenoxyphenyl optionally substituted with any combination of from one to six halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
3-biphenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups, or
3-benzylphenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups.
Preferred compounds of the invention are those compounds of formula V wherein
Ar is phenyl optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups;
R is hydrogen, C1-C4alkyl, C1-C4haloalkyl, C3-C6cycloalkyl or C3-C6halocycloalkyl;
Ar1 is 3-phenoxyphenyl optionally substituted with any combination of from one to six halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups,
3-biphenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups, or
3-benzylphenyl optionally substituted with any combination of from one to five halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups.
More preferred compounds of the invention are those compounds of formula V wherein
Ar is phenyl optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups;
R is isopropyl or cyclopropyl; and
Ar1 is 3-phenoxyphenyl optionally substituted with any combination of from one to six halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups.
Particularly preferred compounds of the invention are those formula V compounds wherein
Ar is phenyl optionally substituted with any combination of from one to three halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups;
R is cyclopropyl; and
Ar1 is 3-phenoxyphenyl optionally substituted with any combination of from one to six halogen, C1-C4alkyl, C1-C4haloalkyl, C1-C4alkoxy or C1-C4haloalkoxy groups.
Moreover, particular preference is given to compounds of formula Ixe2x80x2 and Vxe2x80x2, resp. wherein the variables have the meanings given in table A:
With due modification of the starting compounds, the protocols shown in the synthesis examples below were used for obtaining further compounds I and V.